Apparatus and method for arc welding



May 10, 1960 R. A. NOLAND ET AL 2,936,363

APPARATUS AND METHOD FOR ARC WELDING Filed Jan. 27, 1956 v 4Sheets-Sheet 1 IN VEN TOR.

May 10, 1960 R. A. NOLAND ET AL ,3

APPARATUS AND METHOD FOR ARC WELDING Filed Jan. 27, 1956 4 Sheets-Sheet2 INVENTOR. Robe/'6 E/Vola/zd By Car/61.6. Stone M eafi b [4M 4 6'6)Ytjofflej R. A. NOLAND ET AL APPARATUS AND METHOD FOR ARC WELDING May10, 1960 Filed Jan. 27, 1956 4 Sheets-Sheet 3 d R m m m J m 0 0 a.\U-\\-\QU V I a fl usTwmw m g c. 4 a z a Z 4 g b o o e B c 3 ESN W 5QLI q a. q MFDS NQx KUQO Su s Raw F Wm 0.0%. q 0.38m NM $56 RS May 10,1960 R. A. NOLAND ET AL 2,936,363

APPARATUS AND METHOD FOR ARC WELDING Filed Jan. 27, 1956 4 Sheets-Sheet4 Chamber Pressure Tune 1/: 560012615 IN V EN TOR. Robefl E Nola/1d yCeca! C. Sta/3e United States Patent 2,936,363 APPARATUS AND Msrnon nonARC wnrnme Robert A. Noland, Chicago, and Cecil C. Stone, Himsdale,Ill., assignors to the United States of America as represented by theUnited States Atomic Commission Application January 27, 1956, Serial N0.561,966 *3 Claims. Cl. 219-123 so that a weld is produced simultaneouslyover all points,

of an annular or closed path.

The present application provides an improvement in the means forcreating the magnetic field for rotating the welding arc, aswell as anarrangement for controlling the pressure of the atmosphere in which thewelding is performed, whereby outgassing from the article being weldedis minimized.

The present method and apparatus are particularly useful in welding shuta container for an object, for example, an aluminum jacket for anuclear-fuel slug. When a jacket is welded shut by rotation of anelectric are at very high speed about the jacket in accordance with theteachings of the said Lingafelter application, any outgassing from thejacket due to welding heat will tend to occur through the weld as it isbeing produced, .since the weld is produced simultaneously at allpoints.

The present invention inhibits outgassing from the jacket I being weldedby adjusting the pressure throughout the welding cycle to establish abalance between the gas pres- :sure within the jacket and that of theatmosphere surrounding the jacket.

The present invention also involves an improved control of the magneticfield producing rotation of the welding arc, whereby this rotation isprevented from splash- .ing about the metal being welded as the weldingarc .makes it molten.

In the drawings:

Fig. 1 is a vertical sectional view through the novel :welding apparatusof the present invention;

Fig. 2 is a plan view, partly in section, of the welding apparatus;

Fig. 3 is a sectional view of a welding electrode and .associatedportions of the welding apparatus;

Fig. 4 is a diagrammatic view showing how the weldjing apparatus isoperated and controlled; and

Fig. 5 is a graphical representation of pressures and currents employedin a typical welding cycle used in the present invention.

The novel welding apparatus of the present invention includes a core ofa magnetic metal such as soft iron.

The core 10 fits in a copper sleeve 11 which has its upper end securedto the core 10 as by silver brazing as indicated at 12. The core 10extends through a Pyrex glass plate 13 and is supported thereon by aflange 13a.

The plate 13 is supported on the top plate 13b of a housing 14 andcloses an opening 15 therein.

The lower end of the core 10 receives in a threaded connection the largeend of an adapter nipple 16 formed of a magnetic material such as softiron. The large end ice of the nipple also has a threaded connectionwith a washer 17 of nonmagnetic material such as brass which is securedas by soldering or welding to the lower end of the core 10 and to thelower end of the sleeve 11 in which it is set. The small end of thenipple 16 goes through a spacer 18 of nonmagnetic material such as brassand has a threaded connection with an annular welding electrode 19formed of a suitable refractory material such as molybdenum, tungsten,or graphite.

The spacer 18 rests upon the interior of a base 20 of a magneticconcentrator 21 having the shape of a cup and being formed of a magneticmaterial such as soft iron. The spacer 18 is positioned in thecounterbore of a central opening 22 in the cup base 21 so that the core10 and the welding electrode 19 are held concentric with the opening 22and spaced from the cup base 20.

A spool 23 of a nonmagnetic material such as brass is positioned in thecup '21 so that a loWer end 24 of the spool 23 is secured above and inspaced relation to the cup base 23 by means of screws 25 and spacingwashers 26. A tubular shank 27 of the spool 23 closely fits the exteriorof the sleeve 11, and an upper end 28 of the spool has a collar 29through which set screws 30 are threaded against the sleeve 11. Theinner sides of the ends 24 and 28 and the exterior of the tubular shank157 of the spool 23 are coated with suitable layers 31 of insulatingmaterial such as polystyrene. A coil 32 of insulated wire is wound onthe spool 23 and has most of its length within walls 33 of the cup, onlythe portions of the coil 32. adjacent the upper end 28 of the spool 23projecting beyond the cup walls 33. Current is supplied to the coilthrough a plurality of posts 33a secured to and extending through theplate 13 in gas-tight connections.

The upper portion of the core 10 has two longitudinal passages 34 and 35which may be formed by drilling from above and thereafter closed attheir upper ends by soft-iron plugs 36 which are attached as bysoldering or welding. Inlet line 37 and outlet line 38 are attached tothe core 10 at the upper portions of the passages 34 and 35,respectively. The passages 34 and 35 are connected, respectively withtwo spiral passages 39 and 40 which are formed between the interior ofthe sleeve 11 and two exterior spiral grooves on the core 10 extendingfrom the lower ends of the passages 34 and 35 to the lower end of thecore. The lower ends of the passages 39 and 40 open into an annularspace 41 formed between the washer 17 and the lower ends of the core 10and the sleeve 11. Fig. 1 shows the lower end of the spiral passage 39opening into the annular space 41. In operation of the apparatus of thepresent invention, a coolant such as water enters the core 10 from theinlet line 37, flows successively through the longitudinal passage 34,the spiral passage 39, the annular space 41, the spiral passage 40, thelongitudinal passage 35, and exits from the core 10 through the outletline 38.

The core it is clamped through its flange 13a to the Pyrex plate 13 by aneoprene ring 42, stainless-steel rings 43 and 44, and screws 45. Thering 44 has threaded engagement with the core 10 below the plate 13, andthe screws 45 have threaded engagement with the ring 44 and push thering 43 against the ring 42, which in turn is pressed against the Pyrexplate 13. The core 1% has a relatively good fit with the opening in theplate 13 through which it extends, but sealing at this opening isasaasea top plate 13b of the housing, a neoprene ring 47 on top of theplate 13, and a stainless-steel ring 4? acting against the ring 7, andscrew 49 extending through the ring 48 into engagement with top plate13!).

Welding current is supplied to the electrode 19 through the core from aconductor 50 which is connected to the upper end of the core 16 by beingclamped between a ring 51 and a nut 52. The ring 51 is wedged againstconical surfaces on the plugs 36 and adjacent portions of the core 10,and the nut 52 has threaded engagement with the upper end of the core10.

The core 10 has a longitudinal central opening 53 through which aspecial gas such as chlorine or argon may be supplied from a line 54which is connected to the upper end of the 'core 10. The special gasexits from the lower end of the core through a longitudinal centralopening 55 in the adapter 16 into the welding electrode 19 and isadapted to improve the quality of the welding arc.

The housing 14 is formed of stainless steel and includes, in addition tothe top plate 13b, a tubular body member 56, a bottom plate 57, and aplurality of supporting legs 58 extending downwardly therefrom andsecured thereto as by welding. The tubular member 56 is secured to thetop plate 13b and the bottom plate 57 as by welding. The bottom plate 57has an opening 5 which is closed by a disk 69 which is secured to thebottom plate 57 by a ring 61, threaded members 62 passing through thering 61 and having threaded engagement with the bottom plate 57, andnuts 63 on the threaded members 62. A neoprene ring 64, positioned in anannular groove in the bottom plate 57, seals the opening 59.

A slotted collet 65, which may be formed of brass or bronze, is securedto the disk 60 as by soldering or welding and is adapted to support anassembly 66 to be welded, which may, as shown in Fig. 3, comprise a slugor core 66a of nuclear fuel, an aluminum can 66b, and an aluminum endclosure 66c resting in the open end of the can against the slug. AnInvar collar 67 rests on the upper end of the collet 65 and embraces theportion of the assembly 66 adjacent its upper end. A ring 68 which isformed of a ceramic such as a fired magnesium silicate surmounts thecollar 67 and surrounds the assembly 66.

The housing 14 is provided with two Pyrex viewing windows 69 and 70which are spaced from one another about 90 about the housing so that theeifects of parallax are minimized. The window 69 is clamped by rings 71and 72 between seals 73. Screws 74 hold the rings 71 and 72 together.The ring 71 is secured by soldering or Welding to a short tubularsection 75, which is in turn soldered or welded to the tubular bodymember 56 of the housing 14. The window 70 is clamped by rings 76 and 77between seals 78. The ring 76 is secured by soldering or welding to ashort tubular section 79, which is soldered or welded to the tubularbody member 56. The ring 77 is pivotally mounted at one side by a strap80 on the ring 76, and at the other side a bolt 81 and a nut 82 thereinreleasably clamp the ring 77, seals 78, and window 70 to the ring 76 sothat access to the interior of the housing 14 may be had at this region.The bolt 81 is pivotally mounted on the ring 76 so as to be moved in andout of notches 33 and 84 on the rings 76 and 77. An inlet line 85 and anexhaust line 86 are secured to the tubular body member 56 of the housing14 and serve, respectively, to supply an inert gas such as argon orargon and helium to the housing and to exhaust the housing of air andother gases.

As shown in Fig. 4, the inlet line 85 is provided with a valve 37, whichis opened when a solenoid 68 is energized by an electric current. Whenthe valve 87 is open, a pump 89, connected to the line 85, supplies thehousing 14 with argon or a mixture of helium and argon. The exhaust line86 is provided with a valve 90 which is open when current flows througha solenoid 91. When the valve is open, a vacuum pump 92, connected tothe line 86, reduces the gas pressure in the housing 14.

in operation, a welding arc is struck between the welding electrode 19and the upper end of the assembly 66. There is a radial field set upbetween the core 10 and the concentrator cup 21 across its opening 22because of the flow of current through the coil 32, which held causesthe arc to move at a very high speed around the welding electrode 19.The welding arc, following the ring shape of the welding electrode,creates a weld between the edge of the aluminum end closure and the openend of the aluminum can of the assembly 66, which weld is of annularshape. The movement of the welding are about the welding electrodefollows the right-hand rule of electricity, according to which thecurrent of the welding arc flows axially between the welding electrode19 and the assembly 66, the magnetic field set up by the coil 32, thecore 10, and the concentrator cup 21 acts radially and thus at rightangles to the flow of welding current, and consequently the welding arcis propelled at right angles to the axial direction of the weldingcurrent and at right angles to the radial field, or in other Words,tangentially of the Welding electrode.

The actual welding cycle is like that depicted in Fig. 5 and is causedto occur by virtue of the control apparatus shown in Fig. 4. Accordingto Fig. 5, the pressure in the housing 1.4 is to be lowered to about 5lbs. gage from atmospheric or +5 lbs. gage, depending on whether thehousing 14 is opened to atmosphere for the insertion of a new assembly66 to be welded or a plurality of assemblies 66 are successively weldedin the housing 14. When the pressure in the housing 14 reaches -5 lbs.gage (and it is anticipated that this may occur in about two secondswith the present apparatus), the welding arc is struck and currentstarts to flow through the field coil 32. For four seconds the pressureof the housing 14 is maintained at -5 lbs. gage, and the field currentis maintained at some relatively high value such as 2.5 amperes. At thistime, since it is presumed that the assembly 66 will have become moltenat the outer region where the arc has been directed, the field currentis reduced at once to some relatively low value such as 0.5 ampere andthe pressure in the chamber 14 is increased in a period of two secondsfrom 5 lbs. gage to +5 lbs. gage. Thereupon, both welding current andfield current are cut ofi.

Since the metal being welded becomes molten and can splash outward underthe influence of the rotating welding arc, the field current, whichcauses rotation of the welding arc, is reduced at some convenient timein the six-second welding cycle such as at the elapse of four seconds.As the assembly 66 being welded heats up during the course of thewelding cycle, the gases trapped in the assembly 66 also heat up andtend to escape at the portions being welded because of increase inpressure due to heating. To prevent the outgassing of trapped gasesthrough the weld, which outgassing will seriously reduce the quality ofthe weld, the pressure of the gas in the housing 14 outside of theassembly 66 being welded is increased to balance the increase inpressure of the trapped gases. It is convenient to start this increasein pressure of the welding atmosphere at the elapse of four seconds inthe six-second welding cycle and to double this pressure. It is morepractical to double this pressure by the use of 5 lbs. gage and +5 lbs.gage than to use pressures of one and two atmospheres, for in the firstcase doubling is achieved with 10 and 20 lbs. absolute, in contrast with15 and 30 lbs. absolute in the second case.

Direct welding current is employed and the assembly 66 being welded ismade negative, so that ions move away trom' the assembly 66, thusautomatically cleaning aluminum oxide from the assembly, which wouldtend to interfere with welding.

The Invar collar 67, positioned about the upper portlon of assembly 66during welding, is particularly useful when the aluminum can beingwelded is very thin, for the ring, by chilling and supporting thealuminum can, prevents sagging of the can wall due to the heat ofwelding. The collar 67, being of Invar and thus not expanding as thealuminum can expands, gives the can very good support and helps toprevent: the escape of entrapped gases. The ceramic ring 68, positionedon the Invar collar 67, prevents preferential arcing across the Invarring.

When an assembly 66 is being loaded through the opening 59 in the bottomplate 57 of the housing 14, the appropriate gas for the weldingatmosphere may be flowed through the inlet line 85 so that less timewill be consumed in purging the housing 14 before a welding cycle.

As shown in Fig. 4, the welding cycle is initiated by closing of aswitch 93, so that current flows from the source of control power, whichpreferably supplies alternating current, through closed switch 94 and aswitch 95 closed across contacts 96 to the solenoid 91 which opens thevalve 90 and connects the housing 14 to the vacuum pump. Once closed,the switch 93 stays closed because of energization of a solenoid 96a dueto closing a circuit that includes cam-controlled contacts 96b and aswitch 96c moved with the switch 93. Switch 94 is closed at this time,because it is controlled by a pressure-responsive element 97, which isconnected to the housing 14 and is adapted to open the switch 94 onlywhen the pressure in the housing 14 reaches some dangerously high value.Switch 95 is closed across contacts 96, because it is controlled by apressure-sensitive element 98 connected to the housing 14 so as to pullthe switch away from the contacts 96 when the pressure in the housing 14reaches a certain predetermined low pressure such as 5 lbs. gage,illustrated in Fig. 5.

When this predetermined low pressure is reached, the element 98 snapsthe switch 95 from contacts 96 to contacts 99, where the switch 95 isheld, because a solenoid 99a is energized through closing of a circuitincluding cam-operated contacts 100 and a switch 100a movable with theswitch 95. The result of moving the switch 95 from the contacts 96 is todeenergize the solenoid 91, whereupon the valve 90 is closed, preventingfurther reduction of pressure in the housing 14. The

result of establishing contact between the switch 95 and the contacts 99is to close a circuit through contacts 100 and a solenoid 101, which isnow energized by the voltage of the control-power source and thus closesa switch 102. Closing of switch 102 welding source across the weldingelectrode 19 and the assembly 66 to be welded and across a solenoid 103.The resulting energization of the solenoid 103 closes a switch 104 sothat the high-frequency unit is connected with the source of controlpower through the closed contacts 100 and through switch 95 and contacts99. Thus a high-frequency voltage is imposed across the weldingelectrode 19 and the assembly 66, initiating a welding arc thereacross.The welding arc lowers the voltage across the electrode 19 and theassembly 66 and across the solenoid 103 so that the switch 104 opens anddisconnects the high-frequency unit. At the same time a circuit isclosed through the A.C.-D.C. converter, which brings current ofrelatively high value to the field coil 32 through closed contacts 105.Now the welding arc moves around the welding electrode 19 under theinfluence of the radial field through the concentrator cup 21.

At the same time current flows to a motor 106 which drives a cam 107 inthe direction indicated. After four applies the voltage of the seconds alobe 108 on the cam reaches a roller follower 109, causing an arm 110carrying the follower to open the contacts 105 and to close contacts111, one of each set of contacts 105 and 111 being connected to the arm110. The result of opening the contacts 105 is that the field currentmust now flow through a variable resistance 112 and so is appreciablyreduced. The result of closing contacts 111 is that current now flowsthrough the solenoid 88 which opens the valve 87 and the pump 89 isconnected to the housing 14 to increase the pressure of the gas therein.

When six seconds have elapsed, the earn 107 has rotated far enough tobring the lobe 108 of the cam to a roller follower 113 which is carriedby an arm 114 on which one of each of the pairs of contacts 96b and 100is mounted. Riding of the roller follower 113 on the cam lobe 108 causesopening of contacts 100, which produces a number of results. Thesolenoid 88 is no longer energized, and the valve 87 is closed shuttingoff the housing 14 from supply of gas by the pump 89. The solenoid 101is no longer energized, and the switch 102 is opened, cutting off thewelding are between the welding electrode 19 and the assembly. TheA.C.-D.C. converter is cut oif from the source of control power, and sothe current to the field coil 32 is cut olf. The soleniod 99a is nolonger energized, and the superatmospheric pressure in the housing 14causes the pressure-sensitive element 98 to move the switch 95 away fromthe contacts 99. Riding of the roller follower 1 13 on the cam lobe 108causes opening of contacts 96b, and so the solenoid 96a is deenergized,permitting the manual switch 93 to snap back to starting position.

After driving of the motor 106 is interrupted by opening of the contacts100, the motor and the cam are rotated backwards under the action of aspring 115 until one end of the cam lobe 10$ engages a step 116. Thespring 115, which has its inner end fixed and its outer end connected tothe earn 107, was wound up in the rotation of the cam in the directionof the arrow, and so the unwinding force in the spring is utilized toreverse the rotation of the motor 106 and the cam.

In the embodiment illustrated, the annular electrode 19, theconcentrator opening 22, and the assembly 66 are circular, and the weldproduced on the assembly 66 is circular in outline. However, it is to beunderstood that the weld may have some other outline, for example, anoncircular curved shape such as an ellipse or a noncurved shape such asa regular or irregular polygon. The annular electrode 19 will have theshape desired on the annular weld, and it may be desirable to modify theshape of the concentrator opening 22 to conform to or to approach themodified shape of the annular electrode for facilitating the formationof the modified weld outline. The important thing is that the weld beproduced in a closed or annular path.

The intention is to limit the invention only within the scope of theappended claims.

What is claimed is:

l. A welding machine comprising a magnetic cup having a central openingin its base, a magnetic core extending from the central opening inalignment therewith within the cup and out of contact therewith, anannular welding electrode attached to one end of the core so as to bepositioned in the central opening out of contact with the cup and toextend no more than a small amount beyond the exterior of the base ofthe cup, and a field coil surrounding the core and lying within the cup.

2. The welding machine specified in claim 1 and further comprising apressurizable housing enclosing the cup, core, electrode, coil andworkpiece, whereby'the pressure of the welding atmosphere in the housingmay be below atmospheric at the start of the welding process and may beabove atmospheric at the end of the welding process.

3. An apparatus for creating an annular weld between '7 8 an end closureand the open end of a can containing can become :hot, and means forsimultaneously reducing a fuel slug, said apparatus comprising anannular weldthetstrength of the radial magnetic field. ing electrode,means for striking a welding are between the electrode and the edge ofthe end closure, a gas- References Cited in the-file of this patenttight enclosure for the electrode and the assembly of 5 fuel slug, can,and end closure, means for supplying 21 UNITED STATES PATENTSnonoxidizing gas to the enclosure at a pressure below 510,777 CofiinDec. 12, 1893 atmospheric, means for rotating the are about the edge515,652 vCoffin Feb. 27, 1894 of the end closure by applying a radialmagnetic field 1,711,151 Lincoln Apr. 30, 1929 transversely across theare, means for increasing the 10 1,906,496 Stine et a1. May 2, 1933pressure of the nonoxidizing gas to above atmospheric 2,028,780 Ito Jan.28, 1936 as the edge of the end closure and the open end of the2,743,342 Bettis Apr. 24, 1956

